Some engines include a variable valve train module which controls valve lift through hydraulic operation. This module can include a valve control block positioned on one or more cylinder heads of an engine. The valve control block can include various spaces for components and cavities for hydraulic fluid which together control valve timing and lift. Hydraulic valve control systems provide fully variable valve lift capabilities, which promotes engine efficiency (e.g., through precise variable valve actuation and timing depending on the situation).
During operation of the hydraulic valve control system, a high pressure chamber is periodically pressurized and drained. This allows the fluid in the chamber to be used as hydraulic pushrod to open the valve when needed or as a disconnection which produces zero or limited lift. However, the nature of the operation may produce pressure fluctuations which are severe enough to produce undesirable engine noise. For example, the cyclical changes in pressure could produce a forcing function input which is a source of vibration for the engine and nearby components.
The present disclosure is directed to overcoming one or more problems of the prior art, including providing the advantages of a hydraulic valve control system without producing engine noise.